U.S. patent number 5,928,287 [Application Number 08/981,647] was granted by the patent office on 1999-07-27 for acetabular cup and surgical instrument for implanting same.
This patent grant is currently assigned to Waldemar Link (GmbH & Co.). Invention is credited to Arnold Keller.
United States Patent |
5,928,287 |
Keller |
July 27, 1999 |
Acetabular cup and surgical instrument for implanting same
Abstract
Arrangement consisting of an acetabular cup prosthesis and of an
implantation instrument for same. The acetabular cup prosthesis has
at least one undercut holding recess in its edge end face. The
instrument has a block which fits with centring into the opening or
onto the opening edge of the acetabular cup prosthesis, and at
least one holding projection positionally assigned to the holding
recess and fitting into the latter, which holding projection is
movable transverse to the opening direction, can be locked in a
position in which it catches in the undercut of the holding recess,
and can be withdrawn therefrom by means of an actuating member.
Inventors: |
Keller; Arnold (Kayhude,
DE) |
Assignee: |
Waldemar Link (GmbH & Co.)
(DE)
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Family
ID: |
8023785 |
Appl.
No.: |
08/981,647 |
Filed: |
January 7, 1998 |
PCT
Filed: |
May 09, 1997 |
PCT No.: |
PCT/EP97/02399 |
371
Date: |
January 07, 1998 |
102(e)
Date: |
January 07, 1998 |
PCT
Pub. No.: |
WO97/42915 |
PCT
Pub. Date: |
November 20, 1997 |
Foreign Application Priority Data
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May 9, 1996 [DE] |
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29608453 U |
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Current U.S.
Class: |
623/22.21;
606/91 |
Current CPC
Class: |
A61F
2/4609 (20130101); A61F 2002/30523 (20130101); A61F
2/34 (20130101); A61F 2002/30484 (20130101); A61F
2002/30429 (20130101); A61F 2/4603 (20130101); A61F
2002/30797 (20130101); A61F 2220/0025 (20130101); A61F
2002/30505 (20130101); A61F 2002/4619 (20130101); A61F
2/4684 (20130101); A61F 2002/30803 (20130101); A61F
2002/3611 (20130101) |
Current International
Class: |
A61F
2/46 (20060101); A61F 2/00 (20060101); A61F
2/30 (20060101); A61F 2/32 (20060101); A61F
2/36 (20060101); A61F 2/34 (20060101); A61B
017/58 (); A61B 017/16 () |
Field of
Search: |
;623/22,18
;606/73,81,91 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 303810 |
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Jul 1988 |
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EP |
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0 453694 |
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Apr 1990 |
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EP |
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2281095 |
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May 1976 |
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FR |
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2663840 |
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Jan 1992 |
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FR |
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2676172 |
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Nov 1992 |
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FR |
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2721502 |
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Dec 1995 |
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FR |
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WO 94/21199 |
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Sep 1994 |
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WO |
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WO 95/11641 |
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May 1995 |
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WO |
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Primary Examiner: Willse; David H.
Assistant Examiner: Jackson; Suzette
Attorney, Agent or Firm: Medlen & Carroll, LLP
Claims
I claim:
1. An apparatus comprising:
a) an acetabular cup prosthesis having a cavity and an end face,
wherein said end face contains at least one undercut recess;
and
b) an implantation instrument having:
i) a block capable of engaging said cavity of said acetabular
cup,
ii) at least one holding projection capable of engaging said at
least one undercut recess of said acetabular cup, and
iii) an actuator member capable of engaging and disengaging said
acetabular cup and said implantation instrument, and
wherein in a first position, said actuator member engages said at
least one holding projection with said at least one undercut
recess, and in a second position, said actuator member disengages
said at least one holding projection from said at least one
undercut recess.
2. The apparatus of claim 1, further comprising a spring capable of
locking said at least one holding projection in said undercut
recess.
3. The apparatus of claim 1, further comprising a hand grip, and
wherein said actuator member is contained within said hand
grip.
4. The apparatus of claim 1, wherein said implantation instrument
further comprises a collar positioned parallel to the end face of
said acetabular cup.
5. The apparatus of claim 1, wherein said at least one holding
projections further comprises a hook.
6. The apparatus of claim 1, wherein said at least one recess is
bored at an angle to the planes of said end face and said recess of
said acetabular cup, to produce recessed bores.
7. The apparatus of claim 6, wherein said recessed bores further
have a circumferential fluting.
8. The apparatus of claim 7, wherein said circumferential fluting
comprises threads.
9. The apparatus of claim 1, wherein said implantation instrument
further comprises a first radial slide guide, a second radial slide
guide, a first slide piece, and a second slide piece.
10. The apparatus of claim 9, wherein said first and second radial
slide guides are positioned on said block.
11. The apparatus of claim 10, wherein said first slide piece is
positioned on said first slide guide, said second slide piece is
positioned on said second slide guide, and said holding projections
are arranged on said first and second slide pieces.
12. The apparatus of claim 11, wherein said implantation instrument
further comprises a gear arrangement positioned between said slide
pieces, and an actuating shaft pivotably mounted in a connecting
bar positioned on said head, wherein said connecting bar connects
said head to said actuator member.
13. An apparatus comprising:
a) an acetabular cup prosthesis having a cavity and an end face,
wherein said end face contains at least one undercut recess;
and
b) an implantation instrument having:
i) a block capable of engaging said cavity of said acetabular
cup,
ii) at least one holding projection capable of engaging said at
least one undercut recess of said acetabular cup, and
iii) an actuator member capable of engaging and disengaging said
acetabular cup and said implantation instrument,
iv) a first slide piece positioned on a first slide guide, and a
second slide piece positioned on a second slide guide,
v) a gear arrangement positioned between said first and second
slide pieces, and
vi) an actuating shaft pivotably mounted in a connecting bar
positioned on said head, wherein said connecting bar connects said
head to said actuator member, and
wherein in a first position, said actuator member engages said at
least one holding projection with said at least one undercut
recess, and in a second position, said actuator member disengages
said at least one holding projection from said at least one
undercut recess.
14. The apparatus of claim 13, further comprising a spring capable
of locking said at least one holding projection in said undercut
recess.
15. The apparatus of claim 13, further comprising a hand grip, and
wherein said actuator member is contained within said hand
grip.
16. The apparatus of claim 13, wherein said implantation instrument
further comprises a collar positioned parallel to the end face of
said acetabular cup.
17. The apparatus of claim 13, wherein said at least one holding
projections further comprises a hook.
18. The apparatus of claim 13, wherein said at least one recess is
bored at an angle to the planes of said end face and said recess of
said acetabular cup, to produce recessed bores.
19. The apparatus of claim 13, wherein said recessed bores further
have a circumferential fluting.
20. The apparatus of claim 19, wherein said circumferential fluting
comprises threads.
21. A method for implanting an acetabular cup prosthesis into an
acetabulum, comprising the steps of:
a) providing the apparatus of claim 1, and an acetabulum,
b) contacting said acetabular cup prosthesis with said implantation
instrument in a manner such that said acetabular cup prosthesis is
held on said implantation instrument; and
c) contacting said acetabulum with said acetabular cup prosthesis
held on said implantation instrument.
22. The method of claim 21, further comprising the step of
disengaging said implantation instrument from said acetabular cup
prosthesis, under conditions such that said acetabular cup
prosthesis remains in contact with said acetabulum.
Description
For implanting acetabular cup endoprostheses into the acetabulum,
which may optionally have been provided with a bed of cement,
instruments are normally used which have, at the end of a gripping
rod, a holding head which, for the purpose of holding the cup in a
predetermined relative position to the instrument, has a block,
engaging in the matching cavity of the cup, and a collar which
bears on the edge of the cup. The force necessary for pressing the
cup into the acetabulum can thereby be transmitted easily to the
cup. However, it is desirable that the cup is also held securely on
the instrument in the opposite force direction and in the direction
of rotation, and that it can be released from the instrument again
without transmitting appreciable forces.
For this purpose, a known implantation instrument (FR-A-2,721,502),
on which the wording of the preamble of claim 1 is based, has a
block which grips in the acetabular cup and which is adapted
exactly to the shape of the opening forming the cavity, and holding
pins which are arranged axially parallel on the collar and engage
in holding openings which are designed as axially parallel bores on
the front face of the acetabular cup. The latter is held on the
instrument via the block and the holding pins by means of
frictional forces. For its removal, a plunger which is axially
displaceable counter to a spring force by means of an actuating
member forces the instrument off from the acetabular cup. The
disadvantage is that the acetabular cup is held on the instrument
only via the unreliable frictional engagement, which has to be made
very powerful so that the desired holding force is obtained even in
the event of the coming-together of most unfavourable tolerance
deviations. For release, a comparatively great force, overcoming
the holding force, must be applied, generally greater than the
desired holding force. The greater the force that has to be applied
for release, the more difficult it is to hold the instrument
steady.
An implantation instrument which likewise holds the prosthesis by
frictional force is known from U.S. Pat. No. 5,169,399. This
comprises a head which is adapted to the shape of the cavity of the
acetabular cup and whose halves are pressed away from each other
and against the inner wall of the acetabular cup by a spring force.
To release the instrument from the acetabular cup, the halves of
the head are moved towards each other using an actuating lever, so
that the contact with the acetabular cup is eliminated. In view of
the low coefficient of friction of the inner face of an acetabular
cup, the force with which the halves of the head of this
implantation instrument are pressed against the inner face of the
acetabular cup, and which has to be applied as releasing force when
removing the instrument, must be greater than the desired holding
force. The disadvantages of this device therefore correspond to
those mentioned above. In addition to this, there is only
unsatisfactory protection against unwanted turning of the
acetabular cup on the instrument.
In the case of another known implantation instrument (WO94/21199),
radially arranged holding projections engage in holding openings on
the inner side of the acetabular cup. An intermediate piece is
attached to the instrument, the latter having a block fitting with
centering in an opening in the base of the prosthesis, on which
intermediate piece there are holding projections which are movable
transverse to the opening direction, engage with a spring force in
the holding openings, and can be withdrawn from these by means of
an actuating member. This arrangement is disadvantageous because
the openings in the inner face of the prosthesis are generally
undesirable and demand a greater wall thickness of the prosthesis
at an anatomically unfavourable location.
For the purpose of holding acetabular cup reamers, instruments are
known (U.S. Pat. No. 5,171,313, FR-2,281,095) which engage with
radially arranged holding pins in openings on the inner side of a
reamer head and which can be withdrawn counter to a spring force by
means of an actuating member. The use of such instruments for
holding implants would be disadvantageous for the reason mentioned
in the previous paragraph.
In the case of an instrument for releasing implanted acetabular cup
prostheses (U.S. Pat. No. 5,112,338), radially arranged holding
projections engage in slots on the end face of the acetabular cup.
Since the slots are open towards the front, it is not possible to
hold the acetabular cup on the instrument.
For implanting a bearing dish for a joint cup which is anchored
cementlessly in the acetabulum with the aid of spikes which are
arranged on elastic tongues, an implantation instrument is known
(EP-A-453,694) which is designed specially such that the tongues
are drawn inwards during the implantation by the instrument, so
that the spikes do not interfere with the implantation movement of
the bearing dish to the desired position. When this position has
been reached, the tool is released, so that the tongues once again
assume the outer position and the spikes penetrate the surrounding
tissue in order to fix the bearing dish in place. Since the
tongues, and the openings cooperating with the instrument, are
arranged deep in the bearing dish, the known arrangement does not
provide any indication of how it is possible to avoid the
engagement of the instrument in the cavity of the cup.
Starting from the instrument known from FR-A-2,721,502, the
invention is based on the object of providing an arrangement which
consists of implantation instrument and cup and in which the
instrument engages on the end face of the cup and, nevertheless,
allows reliably reproducible holding forces to be exerted, and in
which the instrument can be easily released from the cup. The
solution according to the invention lies in the features of claim
1.
The acetabular cup has in its edge end face at least one holding
recess which is undercut in relation to the opening direction. The
opening direction is that direction in which the acetabular cup
opens out. It is also the direction in which the instrument is to
be removed from the acetabular cup, based on the direction of the
cooperating surface parts of instrument and acetabular cup. This is
generally the direction normal to the plane in which the edge end
face lies.
The instrument has a block which fits with centering into the
opening or onto the opening edge of the acetabular cup. It
additionally has at least one holding projection which is
positionally assigned to the holding recess of the acetabular cup
and accordingly can be introduced into the holding recess. It is
designed such that it can engage in the undercut of the holding
recess. It can be locked in this position. It can be withdrawn from
the locked position by means of a special actuating member. Two or
more holding projections and holding recesses are generally
provided, distributed uniformly about the circumference so that
their locking forces balance each other. The advantage of this
arrangement lies in the fact that the acetabular cup is held
securely on the instrument, even against application of substantial
forces, so long as the locking of the holding projections in the
holding recesses is not released, and that, however, after the
locking has been released, no tensile forces whatsoever can any
longer be exerted on the acetabular cup when removing the
instrument from the latter. The locking need not be designed in the
manner of a fixed lock, although this is possible; in general it is
sufficient for the holding projections to be held in the locking
position by a spring force, in which case the spring force is
chosen to be so great that it is sufficient, under all practically
occurring conditions, for holding the acetabular cup securely on
the instrument.
The actuating member with which the locking is released is
expediently arranged on a hand grip of the instrument at a location
which is accessible in the normal gripping position. This is
intended to allow the physician to release the instrument without
altering his hand position. This avoids undesired relative
movements being transmitted to the acetabular cup and inadvertently
changing the position of the latter.
The holding projections of the instrument expediently run roughly
in the opening direction and have a hook which is directed sideways
(in relation to the principal direction of the holding projections)
and which engages in the undercut of the openings. This embodiment
is particularly simple if the holding recesses are designed as
bores running at an angle relative to the opening direction, the
angled inclination preferably running outwards or inwards in the
radial direction. Accordingly, the hooks of the holding
projections, and the direction of the locking movement of the
holding projections, are also directed outwards or inwards.
The reliability of the engagement can be further enhanced by the
bores being provided with a circumferential fluting, for example in
the form of a thread. This is especially so when the lateral
extension of the holding projection has an edge or several edges
cooperating with the fluting.
So that the holding projections of the instrument can be moved
transverse to the opening direction of the acetabular cup, they are
expediently arranged on slide pieces which are guided in
essentially radial slide guides in the tool head. A gear
arrangement can be provided for their movement, this gear
arrangement connecting the slide pieces to an actuating shaft which
is mounted pivotably in a bar arranged centrally on the head and
connecting the latter to the hand grip, and which actuating shaft
bears the actuating member projecting laterally from the connecting
bar. The locking spring can act on the slide pieces or engage on
the actuating shaft.
The invention is explained in more detail below, with reference to
the drawing which represents an advantageous illustrative
embodiment. In the drawing:
FIG. 1 shows the head of the instrument and an acetabular cup in
longitudinal section along the line I--I in FIG. 2,
FIG. 2 shows a cross-section through the head of the instrument
along the line II--II in FIG. 1,
FIG. 3 shows a side view of the instrument head in direction III in
FIG. 2, and
FIG. 4 shows an overall view of the instrument.
The instrument consists of the hand grip 1, the instrument head 2,
and a bar 3 which connects these two parts and on which the
actuating member 4 is arranged in such a way that, with the hand in
a normal position, it can easily be actuated counter to a spring
force, in the direction of the arrow, using one finger. By means of
this actuation, the connection to the acetabular cup, previously
held by the instrument, can be released.
The instrument head has a cylindrical block 5 whose diameter is
dimensioned with a certain play matching the size and shape of the
opening of the cup 6 and is fitted into the opening. It
additionally has a collar 8 which is intended to be applied on the
end face 9 of the cup 6. In this way the instrument is aligned with
the opening direction 10 of the cup which, in the examples
represented, coincides with the midline of the cup and of the
instrument.
In the instrument head there are two bores 11 which lie parallel,
with their midpoints symmetrical to each other, in a plane running
perpendicular to the midline 10, and which each contain a slide
piece 12 which is forced towards the outside by a spring 13. On
their side facing the midline, the slide pieces 12 are designed as
toothed racks 14 which cooperate with a centrally arranged pinion
15. The pinion 15 is arranged at the end of a shaft 16 which runs
within the hollow bar 3 and is connected to the actuating member 4.
At the outermost end, it is provided with a stud 17 which is
mounted in a bore 18 of the instrument head. Along the rest of its
course, the shaft is borne by the inner face of the bar 3. By
actuating the actuating member 4 in the direction of the arrow
shown in FIG. 4, the pinion is turned so that the slide pieces 12
are drawn back into the instrument head counter to the action of
the springs 13. When the actuating member 4 is released, these
parts take up the end position represented in FIG. 2.
In the embodiment represented, the slide pieces each have, in a
plane 21 flush with the underside 20 of the collar 8, a holding
projection 22 whose principal direction runs approximately parallel
to the central axis 10 and which has, at the end, a hook 23
pointing approximately radially outwards. Bores 24 are provided in
the end face 9 of the associated cup 6 at corresponding
circumferential positions, which bores 24 run radially outwards,
slightly obliquely, and in this way, as is represented in FIG. 1,
form an undercut (in relation to the axis 10) into which the hook
23 can engage. For connecting the two parts, the slide pieces 12
are drawn back by actuating the actuating member 4. In their inner
end position, the holding projections 22 are situated at
approximately the same radial position as the openings of the bores
24. It is therefore easy to locate the position in which the
instrument and the cup fit together so that the holding projections
22 can engage in the bores 24. The actuating member is then
released; the slide pieces 12 slide approximately radially
outwards, as a result of which the hooks 23 come into engagement
with the undercut of the bores 24. The cup then sits securely on
the instrument because the hooks 23 are locked in their holding
position by the springs 13. The inclination of the bores 24 and the
force of the springs 13 can be readily dimensioned in such a way
that the holding force, with which the hooks 23 are locked in the
holding position, is sufficient for every case of use which may
reasonably arise. The holding force of the hooks 23 in the oblique
bores 24 can be further improved by a fluting (for example a
threaded section) of the bores. It will be understood that the
spacing of the bores 24 from each other is not greater than the
maximum distance between the hooks 23. Once the cup has been
implanted or, for other reasons, has to be released from the
instrument, the actuating member 4 is once again actuated; when
actuated, the holding projections 22 draw radially back and the
instrument can be removed from the cup without any disruptive
forces being exerted on the latter.
The illustrative embodiment shows that the direction of movement of
the holding projections 22 does not have to be exactly radial, but
only needs to have a sufficient component of radial movement. Nor
does the movement need to be executed rectilinearly; instead, it
might possibly involve some kind of swivel movement.
* * * * *